Power transformers and “chargers” are used to power many office and household electronic and electrical devices. They operate by shifting incoming AC wall power to different, usually lower, voltage levels, often using a coil transformer. The coil on the input side is referred to as the primary winding and coil on the output side is referred to as the secondary winding. The secondary winding of a coil transformer is typically followed by a converter, which changes the AC transformer output into a DC signal.
When a device on the secondary side of the transformer or charger requires power, it loads the transformer/charger output. However, even when the device on the secondary side requires no power and presents no load, the transformer primary typically continues to operate. Losses such as resistive losses in the transformer primary coil will consume energy. This approach first came into use before energy conservation became a topical issue. Today these devices are referred to as “energy vampires”. A second type of so-called “energy vampire” is exemplified by a relatively large transformer capable of providing relatively high peak powers, such as, for example, a microwave oven running on “High”. Most of the time, however, the high power capability is not needed but the power transformer is kept continuously running to power other continuously-on functions such as a clock. While instantaneous power losses are low, significant energy consumption accrues over time.
Other forms of “energy vampires” include appliances that are kept pre-heated, such as photocopy machines. It has been estimated that “energy vampires”, in their various forms and configurations, consume roughly 10% of all power generated in the United States. Reducing these losses can directly benefit consumers and power providers alike. Moreover, reducing these losses provides innumerable environmental benefits.
It is recognized that not all power supplies are transformer based. For example, switch-mode supplies operate by using a switching regulator to turn MOSFETs on and off in rapid succession to maintain a predetermined output voltage or current. While these switch mode supplies can lead to more efficient power usage than, for example, a voltage divider in a dimmer switch, they suffer from being frequently more expensive, complex and electrically noisy. Further drawbacks include being slow and/or inaccurate with rapidly changing loads; producing electrical transients that can potentially damage delicate electronics; having a poor power factor: having a reactance that results in inefficient power utilization and not providing high voltage isolation.
The present disclosure addresses at least some of these concerns.